Electrical properties of Al-doped ZnO films fabricated by a hot-cathode plasma sputtering method

A hot-cathode plasma sputtering technique was used to fabricate highly transparent and conducting aluminum-doped zinc oxide (AZO) films on glass substrates from disk shaped AZO (Al2O3: 5 wt.% and 2 wt.%) targets. Using a target voltage VT = −200 V and plasma excitation pressure PAr = 1.5 × 10−3 Torr, the lowest resistivity of 4.0 × 10−4 Ω cm was obtained at 400 nm with a carrier density of 8.7 × 1020 cm−3 and a Hall mobility of 17 cm2/V s. The analyzed structural properties of these films revealed that this lower resistivity was due to a decrease in the lattice spacing d(0 0 2) of the (0 0 2) plane parallel to the substrate surface. This decrease in lattice spacing was presumably caused by oxygen vacancies acting as an effective source of carrier electrons.